Norovirus Main Gastroenteritis Culprit in Kids

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With the reintroduction of rotavirus vaccines, cases of rotavirus-associated acute gastroenteritis have declined.

Norovirus has subsequently become the leading cause of medically attended acute gastroenteritis in U.S. children ages 5 and younger.

Norovirus far surpasses rotavirus as the primary cause of acute gastroenteritis in children younger than 5 following the successful reintroduction of rotavirus vaccines, researchers found.

Based on surveillance conducted in three U.S. counties, norovirus was responsible for acute gastroenteritis in 21% of young children brought for medical attention in 2009 and 2010, according to Daniel Payne, PhD, MSPH, of the CDC's National Center for Immunization and Respiratory Diseases in Atlanta, and colleagues. Rotavirus was seen in just 12% of children in those years.

The norovirus percentage translated into an estimated 14,000 hospitalizations, 281,000 emergency department visits, and 627,000 outpatient visits annually, and those encounters combined accounted for an estimated $273 million in annual treatment costs, the researchers reported in the March 21 issue of the New England Journal of Medicine.

"Given the substantial decline in pediatric rotavirus-associated acute gastroenteritis in the U.S. since the introduction of rotavirus vaccines, and given recent advances in the development of candidate norovirus vaccines, there is a need to directly measure the pediatric healthcare burden of norovirus-associated acute gastroenteritis," they wrote.

Payne and colleagues examined data from the New Vaccine Surveillance Network, which prospectively collects information from the counties in which three centers reside -- the University of Rochester Medical Center in Monroe County, N.Y., Vanderbilt University Medical Center in Davidson County, Tenn., and Cincinnati Children's Hospital Medical Center in Hamilton County, Ohio.

The current analysis included 1,295 children younger than 5 who were treated for acute gastroenteritis at one of those centers in 2009 or 2010 and who underwent testing for norovirus; it also included 493 healthy controls who underwent testing for the virus.

Overall, 21% of the children with acute gastroenteritis -- 22% in 2009 and 20% in 2010 -- tested positive for norovirus. The average age of the children with a positive test was 17 months.

A smaller percentage of the healthy controls -- 4% -- tested positive for norovirus, indicating a low rate of asymptomatic infection in this age group, according to the researchers.

Most of the norovirus samples that were available for genotyping came from the GII genogroup, although there was a shift in the predominant variant from one year to the next. It was GII.4 Minerva in 2009 and GII.4 New Orleans in 2010.

That information "may be helpful in identifying the most appropriate vaccine candidates and in targeting populations for vaccination," according to the researchers.

A lower proportion of children with acute gastroenteritis tested positive for rotavirus during the study period (12%), and the rate dropped substantially from 19% in 2009 to 2% in 2010. Only one healthy control tested positive for the virus.

The drop over time was reflected in substantially lower rates of hospitalizations, emergency department visits, and outpatient visits for rotavirus-associated acute gastroenteritis in 2010 compared with 2009.

In contrast, the rates of hospitalizations, emergency department visits, and outpatient visits for norovirus-associated acute gastroenteritis remained relatively steady from 2009 to 2010:

Hospitalizations: 8.6 per 10,000 children in 2009 and 5.8 per 10,000 in 2010

The researchers acknowledged that the surveillance may not be representative of the larger U.S. population of children younger than 5 and may not accurately reflect the year-to-year variation in disease burden.

The study was supported by a cooperative agreement with the CDC.

Payne reported that he had no conflicts of interest. His co-authors reported relationships with GlaxoSmithKline, Merck, and Luminex Molecular Diagnostics.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner